1. Field of the Invention
This invention relates to a variable resistor with a switch wherein the resistance thereof is adjusted by sliding movement of a slider receiver and a switching operation occurs at a predetermined position of the slider receiver.
2. Description of Prior Art
Variable resistors with a switch are already known wherein the resistance thereof is adjusted by sliding movement of a slider receiver and a switching operation occurs at a predetermined position of the slider receiver.
An exemplary one of such conventional variable resistors with a switch includes a base plate on which a resistance strip and a conductor constituting the switch are disposed in a juxtaposed relationship and a slider receiver to which a slider is secured is mounted for sliding movement covering over the base plate. With the conventional variable resistor with a switch, the resistance thereof is determined or a switching operation thereof occurs in response to a position of the slider relative to the resistance strip and the conductor as the slider receiver is slidably moved.
However, a variable resistor with a switch having such a construction as described just above has a relatively large dimension in its widthwise direction because a resistance strip and a conductor constituting a switch are disposed in a juxtaposed relationship. Accordingly, such a variable resistor with a switch cannot be applied to such a specific application as a car-carried application where there is a spatial limit left for the switch to be allowed to occupy.
Thus, the applicant of the present patent application proposed, in Japanese Utility Model Application No. 60-107570, an electronic component of the slide type which is significantly reduced in dimension in its widthwise direction.
Now, the electronic component of the slide type proposed precedingly by the applicant will be described with reference to FIGS. 10 to 12.
FIG. 10 is a cross sectional view showing construction of essential part of the proposed electronic component, FIG. 11 a perspective view showing construction of a base plate assembly of the proposed electronic component, and FIG. 12 a schematic view illustrating operation of a third switch of the proposed electronic component.
Referring to FIG. 10, a pair of base plates 1 and 2 made of a suitable electrically insulating material are fitted in a pair of upper and lower openings of a housing 3. A pair of shoulders 3a are formed on an inner wall adjacent opposite side edges of the housing 3, and a slider receiver 4 is mounted for sliding movement on each of the shoulders 3a.
The base plate 1 fitted in a lower portion of the housing 3 has a resistance strip 5 and a collector strip 6 provided on an upper face thereof and extending in a longitudinal direction of the base plate 1. A slider 7 having a pair of spring contacts 7a and 7b thereon is mounted on reverse faces, that is, lower faces of the slider receivers 4. The spring contacts 7a and 7b on the slider 7 are normally held in contact with the resistance strip 5 and the collector strip 6, respectively. A pair of terminals not shown are located alongside the base plate 1 and extend in the same direction. The terminals are connected to opposite ends of the resistance strip 5 and also to an end of the collector strip 6, thereby constituting a variable resistor wherein the resistance between the terminals is varied in response to a position of the slider 7.
Meanwhile, as shown in FIG. 11, conductors 9a, 9b and 11a, 11b for two switches are provided in a longitudinal direction on a lower face of the base plate 2 fitted in an upper section of the housing 3 by a suitable means such as printing. Provided on an upper face of the slider receiver 4 are another slider 12 having a pair of spring contacts 12a and 12b provided thereon for sliding movement on the conductors 9a and 9b, respectively, and a further slider 13 having a pair of spring contacts 13a and 13b provided thereon for sliding movement on the conductors 11a and 11b, respectively. Terminals 14a, 14b, 15a and 15b are connected to one ends of the conductors 9a, 9b, 10a and 10b, respectively, and extend in the same direction with the terminals provided on the base plate 1. The conductors 9a and 9b and the slider 12 constitute a first switch means wherein an off or open state in which the conductors 9a and 9b are disconnected from each other occurs when the slider 12 is positioned on an extension line (a left portion in FIG. 11) of the conductor 9a which has a smaller extent than the other conductor 9b. Meanwhile, a roundabout portion W is formed intermediately of the conductor 11a and provides a switch-off region which disconnects the conductors 11a and 11b from each other when the slider 13 is positioned at the switch-off region, but when the slider 13 is slidably moved farther leftwardly in FIG. 11 than the switch-off region, the conductors 11a and 11b are connected to each other, thereby constituting a second switch means.
An actuating member 16 for slidably displacing the slider receiver 4 is located at a portion of the upper base plate 2 remote from the conductors, and an operating rod 17 extends uprightly from the actuating member 16. The actuating member 16 is accommodated in a casing 18 fitted on the housing 3. The casing 18 has a guide slot 19 perforated in parallel with the conductors in a top wall thereof, and the operating rod 17 extends upwardly outwards through the guide slot 19 so that the actuating member 16 may be moved manually or by some other means.
Also the base plate 2 has a guide slot 20 perforated therein in parallel with the conductors. The actuating member 16 and the slider receiver 4 are interconnected by a pair of connecting portions which extend through the guide slot 20 so that the slider receiver 4 may be slidably moved by the actuating member 16.
The actuating member 16 is urged downwardly by a spring member 28 which is fitted around the operating rod 17, located on the actuating member 16 and pressed against an inner face of the casing 18 with a spring receiver 29 interposed therebetween. Consequently, a leg rod is contacted under pressure with a recess 27 of the slider receiver 4.
A third switch means is provided on an upper face of the base plate 2. The third switch means is comprised of a pair of spring contacts 30a and 30b connected to a pair of terminals 29a and 29b, respectively, as shown in FIG. 12. The spring contacts 30a and 30b are normally disconnected from each other but are connected when they are pressed by a pressing portion 31 formed on the actuating member 16.
A click spring 34 is accommodated in a receiving recess 33 formed in a side wall of the actuating member 16, and a click ball 32 is received at an end of the click spring 34 and normally urged by the click spring 34 in a direction to project from the receiving recess 33 and engage with one of a plurality of click grooves 34-1, 34-2, . . . formed on a side wall of the casing 18 in a row in a direction of movement of the actuating member 16 thereby to position the actuating member 16 at its moved position.
With the electronic component of the slide type described above, the widthwise dimension can be reduced significantly, and a switching operation where a relatively low current capacity is required can be assigned to the first and second switch means while a switching operation where a relatively high current capacity is required can be assigned to the third switch means.
However, since the current capacity of the third switch means is high, an arc appears readily between the spring contacts 30a and 30b. Such a tendency is prominent particularly when the operating rod 17 is operated slowly so that switching between the contacts 30a and 30b occurs slowly. Accordingly, it is a problem that the contacts may readily be abraded resulting in an accident of cutoff of the switch.